1. Field of the Invention
The present invention relates to a stacked structure of a power converter configured by connecting power semiconductor modules in parallel.
2. Description of the Related Art
IGBT modules generally require a heat sink for cooling heat due to generation loss. A typical aluminium heat sink is shown in FIG. 9. It usually has a shape of a rectangular solid, is composed of a heat reception part 19 and a fin part 20 and effects cooling by ventilating the fin part 20. Three IGBT modules, according to the example shown in FIG. 7, connected in parallel are placed in the heat reception part as nine modules of all phases or as separate phases each containing three modules, as shown in FIGS. 10 and 11, respectively.
The configuration of IGBT modules containing two elements and examples of closely-positioned three parallel-connected IGBT modules are disclosed in, for example, Japanese Patent Application Laid-open No. 2005-117783.
As described above, in a power converter in which IGBT modules are connected in parallel, the IGBT modules need to be arranged closely to a heat reception part as shown in FIG. 10 in which all nine modules are arranged on one heat sink or FIG. 11 in which each phase containing three modules is arranged on a heat sink, in view of attaining a balance in current between IGBT modules.
However, when the number of parallel-connected modules is increased (e.g. five in the case of FIG. 12), the overall size of a converter may not be reduced as shown in FIG. 13 where three phases are arranged elongated in X (lateral) direction.
On the other hand, when modules are arranged in two rows relative to a ventilation direction, the length in X (lateral) direction can be shortened, as shown in FIG. 14A in which three phases of three parallel-connected IGBT modules are arranged on one heat sink; FIG. 14B in which each phase of three parallel-connected IGBT modules is arranged on each heat sink; FIG. 15A in which three phases of five parallel-connected IGBT modules are arranged on one heat sink; and FIG. 15B in which each phase of five parallel-connected IGBT modules is arranged on each heat sink.
However, when the number of parallel-connected modules is odd, contrary to the case when the number is even, dead space is created as shown in FIGS. 14 and 15 by the dotted line 21 (shown partially; the same applies for the rest), less promoting effective utilization of a heat sink.
When five and four modules are arranged respectively on the windward and leeward sides as shown in FIG. 16 (in the case of three parallel-connected IGBT modules), dead space can be reduced compared to the cases shown in FIGS. 14 and 15. However, because two IGBT modules in the V phase are arranged on the leeward side, those two modules have higher thermal load than the IGBT modules in the other phases, resulting in the requirement for a thermal design based on the V phase.